Try spending time with all the elements. Take a walk in the park, make a bonfire, go swimming, etc. Most people feel comfortable with a certain elements, which they say it's "theirs". If that doesn't work, try meditating. I feel like that solves all problems if you let it.

Keep in mind that you can have more than one element you associate yourself with! So you do not have to narrow it down to one when you are looking. I think Amber did a good job of suggesting some great things. Spending time, meditating, and working with all the elements will give you a better idea of what you are comfortable with and feel best working with. I would even suggest meditating on the elements, or a specific element, before sleeping and keeping a dream journal. Best of luck!